2对多对一关系的mysql外键冲突

Question

I have 3 tables, a Child, a Parent, and a GrandParent. Child has a column (parentId) pointing to Parent (many-to-one relationship). Parent has a column (grandParentId) pointing to GrandParent (another many-to-one). When I insert to GrandParent and Parent, they both work. However, when I insert to Child, it fails with a "foreign key constraint" violation.

   create table Child (
        id bigint not null auto_increment unique,
        attr1 int,
        parentId bigint not null,
        primary key (id)
    );

    create table Parent (
        id bigint not null auto_increment unique,
        attr1 int,
        grandParentId bigint not null,
        primary key (id)
    );
    create table GrandParent (
        id bigint not null auto_increment unique,
        attr1 int,
        primary key (id)
    );

alter table Child 
        add constraint FK102016375B091 
        foreign key (parentId) 
        references Parent (id);

 alter table Parent 
        add constraint FKB99B04C56B478365 
        foreign key (grandParentId) 
        references GrandParent (id);


    insert into GrandParent(attr1) values(1);  # created GrandParent(id)=1 
    insert into Parent(attr1, grandParentId) values(2, 1); #created Parent(id=1)
    insert into Child(attr1, parentId) values(3, 1); #fails

Both GrandParent and Parent rows are created with id=1. Last statement fails with the following error (t1 is a new database).

ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails (`t1`.`child`, CONSTRAINT `FK102016375B091` FOREIGN KEY (`parentId`) REFERENCES `Parent` (`id`))

If I remove the parent to grandparent constraint in the parent table, the 3rd statement works.

Your help appreciated!

Answer 1

Your script is correct, and works for me. But, before the inserting, check the AUTO_INCREMENT option for the Parent table. Is it '1'?

For example, run SHOW CREATE TABLE Parent; statement.